MultiModemDSVD User Guide | C Loopback Tests |
3.Type AT&T1 and press ENTER. This places your modem in analog loopback mode in the originate mode. A CONNECT message should appear on your dis- play. The modem is now out of command mode and in a
4.Note that the CD LED is on. If you are set for 14,400 bps or higher, a speed LED should be on. If the CD LED is not on, there is a defect in your modem.
5.Enter characters from your keyboard. For this test, typing multiple uppercase U characters is a good way to send an alternating test pattern of binary ones and zeros. The characters entered should be displayed on your monitor.
6.To exit the test, type the escape sequence +++AT and press ENTER. This puts the modem in online command mode. Then type either AT&T or ATH to return to command mode.
7.Your modem passes this test if the characters received on your monitor are the same as those entered from your keyboard. If different characters appear on your monitor, your modem is probably causing the problem, though it could also be your computer. If your modem passes this test, but you are receiving er- rors while on line, the remote modem or the phone line could be at fault.
Remote Digital Loopback Test (V.54 Loop 2)
The remote digital loopback test tests the phone lines and the circuits of both your modem and a remote modem. In this test, your modem must be on line with another modem that is set up to respond to a request for remote digital loopback. (Note that some modems might not support remote digital loopback or might have it disabled.) Data from your computer or terminal is transmitted through your modem and over the phone line to the remote modem, where it is then looped back to your modem.
AT&T6
CONNECT 9600
UUUUUUUUUUU
UUUUU
Digital Analog | Analog Digital | |||||
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AT&T4
OK
Computer or Terminal Local MultiModem | Remote MultiModem Computer or Terminal |
Figure C-2. Remote digital loopback test.
Test procedure
1.Arrange to have &T4 set on the remote test modem. This command enables the remote modem to respond to an &T6 request for a remote digital loopback test from the local modem.
2.Open your communications software and go into terminal mode. Type AT and press ENTER; you should get an OK message. Type AT\N and press ENTER to disable error correction. Type AT+MS=9,1,9600,9600 and press ENTER to set the local modem to V.32 mode at 9600 bps.
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